Process for preparing granular ammonium sulfate
阅读说明：本技术 粒状硫铵的制备方法 (Process for preparing granular ammonium sulfate ) 是由 佐藤利雄 李文娟 于 2019-11-07 设计创作，主要内容包括：本发明公开了一种粒状硫铵的制备方法,硫铵的一部分或者全部溶解于水或游离硫酸水溶液后,在游离硫酸和晶体诱导剂的存在下,以银-氯化银电极为比较电极的氧化还原电位在300mV及以下晶析成粒状硫铵。采用本发明提供的方法制得的粒状硫铵大、圆且优质。(The invention discloses a method for preparing granular ammonium sulfate, after dissolving a part or all of ammonium sulfate in water or free sulfuric acid water solution, under the existence of free sulfuric acid and crystal inducer, the oxidation-reduction potential of silver-silver chloride electrode as comparison electrode is crystallized into granular ammonium sulfate at 300mV or below. The granular ammonium sulfate prepared by the method provided by the invention is large, round and high in quality.)
1. A process for producing granular ammonium sulfate, characterized in that after a part or all of ammonium sulfate is dissolved in water or an aqueous solution of free sulfuric acid, granular ammonium sulfate is crystallized from a silver-silver chloride electrode as a comparative electrode at an oxidation-reduction potential of 300mV or less in the presence of free sulfuric acid and a crystal inducer.
2. The method of claim 1, wherein the ammonium sulfate is produced from coke oven gas.
3. The method for producing granulated ammonium sulfate according to claim 1, wherein the concentration of free sulfuric acid at the time of crystallization is 0.1% to 15%.
4. The method for producing granulated ammonium sulfate according to claim 1, wherein ammonium sulfate is dissolved in an acidic ammonium sulfate solution to crystallize the ammonium sulfate.
5. The method for producing granular ammonium sulfate according to claim 1, 2, 3, or 4, wherein the inducer is one or two or more kinds of sulfamic acid or a salt thereof, and the concentration of the inducer is 0.05 to 10% in terms of sulfamic acid.
6. The method of producing granular ammonium sulfate according to claim 1, 2, 3, or 4, wherein the inducer is one or two or more of nitric acid and salts thereof.
7. The method for preparing granular ammonium sulfate according to claim 1, 2, 3 or 4, wherein the inducer is one or more of sulfamic acid or its salts, nitric acid or its salts, citric acid or its salts, oxalic acid or its salts, malic acid or its salts, phosphoric acid or its salts, and urea.
Technical Field
The invention relates to the field of ammonium sulfate fertilizer manufacturing, in particular to a preparation method of granular ammonium sulfate.
Background
When used alone, ammonium sulfate used as a fertilizer is required to be dispersed little in the presence of wind, to be uniformly applied, and not to be attached to leaves and stems. On the other hand, when ammonium sulfate is used in combination with a phosphate fertilizer and a potassium fertilizer, it is necessary to uniformly mix the ammonium sulfate with the phosphate fertilizer and the potassium fertilizer and to have a uniform particle size, and therefore, crystalline ammonium sulfate having a large, round and smooth particle size and a certain hardness (hereinafter referred to as "granular ammonium sulfate" in the present invention) is required, and particularly, the particle size is required to be 2mm to 4mm, the shape of the crystalline ammonium sulfate is required to be spherical, dice-like or rice-like, and the axial ratio (the length of the crystal divided by the diameter of the crystal) is required to be 0.7 to 1.5.
The ammonium sulfate is ammonium sulfate mother liquor obtained by contacting coke oven gas with sulfuric acid solution or ammonium sulfate produced from ammonium sulfate solution obtained by the methods of caprolactam production process, ammonia and sulfuric acid neutralization process and the like. However, most of these ammonium sulfates are powdery or prismatic.
Ammonium sulfate is generally granulated by a granulation method. That is, various methods are known, such as a method of compression molding ammonium sulfate and then pulverizing and granulating the ammonium sulfate (described in
On the other hand, a method of dissolving ammonium sulfate in water and then adding sulfamic acid and a reducing agent or a chelating agent to prepare granular ammonium sulfate (described in patent document 8).
Disclosure of Invention
The granular ammonium sulfate produced by compression molding and pressure granulation is easy to be powdery when being impacted during use, thereby causing the defect of pulverization.
It is therefore an object of the present invention to provide a process for preparing crystalline granular ammonium sulfate which is not easily crushed.
After the inventors studied the above problems, they found that: the ammonium sulfate solution is dissolved in water to crystallize into powder or column, and under certain specific conditions, large, smooth and hard granular ammonium sulfate crystals may be precipitated.
That is, after a part or all of ammonium sulfate is dissolved in water or an aqueous solution of free sulfuric acid, the oxidation-reduction potential of the silver-silver chloride electrode as a comparative electrode is 300mV or less in the presence of free sulfuric acid and an inducer, and the resulting ammonium sulfate is produced into desired granular ammonium sulfate.
The ammonium sulfate used herein may be produced by any method. In addition to powdery ammonium sulfate produced in a process of neutralizing sulfuric acid and ammonia, crystalline ammonium sulfate having a particle size of 2mm or less produced by an industrial crystallization apparatus, slender (or prismatic) ammonium sulfate is not suitable for mixing with other fertilizers or is difficult to use alone, but the object of easy use can be achieved by the method provided by the present invention. In addition, ammonium sulfate obtained by washing coke oven gas with a free sulfuric acid solution is often powdery or poorly shaped crystals (in many cases, prismatic crystals) and is also very suitable as a raw material of the present invention.
The ammonium sulfate in the present invention may be completely dissolved in water or an aqueous solution of free sulfuric acid, but it is not necessarily completely dissolved.
When the ammonium sulfate contains iron as a metal component or a foreign substance, it may be dissolved in water as it is, or may be made into an alkaline filtered metal component or a foreign substance with ammonia or the like. However, since the crystallization by the method of the present invention is less affected by the reduction of the metal element such as iron ions, it is not necessary to remove the metal component such as iron ions in particular.
Some or all of these ammonium sulfates are dissolved in an aqueous solution or an aqueous solution of free sulfuric acid.
Since the free sulfuric acid concentration in the present invention is measured by the method in GB535-1995, hydrochloric acid or the like can be converted to free sulfuric acid in the present invention when GB535-1995 is used as a method for measuring the free sulfuric acid concentration.
The concentration of free sulfuric acid is 0.1 to 15%, preferably 0.5 to 8%.
When the free sulfuric acid concentration is less than 0.1%, fine crystallization is caused as the effect of the inducer is reduced. If the concentration of free sulfuric acid is too high, the concentration of free sulfuric acid in ammonium sulfate crystals becomes high.
The ammonium sulfate mother liquor can be used as an aqueous solution or a free sulfuric acid aqueous solution.
Nitric acid itself has the effect of an inducer, and has the effect of increasing the concentration of free sulfuric acid.
Crystallization is achieved under conditions of an inducer. The inducer may be any known in the art. In particular, sulfamic acid or its salts, nitric acid or its salts, citric acid or its salts, oxalic acid or its salts, malic acid or its salts, phosphoric acid or its salts, urea, and the like. These inducers may be used alone or in combination.
It has been found that the effect of the sulfamic acid or salts thereof is the best. Substances of the sulfamic acid and sulfamic acid salts are: sulfamic acid, ammonium sulfamate, sodium sulfamate, potassium sulfamate, guanidine sulfamate, iron sulfamate, and the like.
When sulfamic acid or its salt is used as inducer, the concentration of sulfamic acid is 0.05-10%, preferably 0.1-5%. The higher the concentration of sulfamic acid, the smaller the axial ratio of ammonium sulfate crystals, the granular ammonium sulfate having an axial ratio of less than 1.0 is produced, but when ammonium sulfate is used as a fertilizer, the quality of ammonium sulfate crystals having an axial ratio of less than 1.0 is not so much improved, and therefore, ammonium sulfate crystals having an axial ratio of not less than 1.0 are preferred for saving the amount of the inducer used.
Most of the added sulfamic acid or sulfamate, especially the acidic ammonium sulfate which is decomposed into sulfuric acid and ammonia by adding water during the drying process of ammonium sulfate and becomes a fertilizer component.
Sulfamic acid or its salts can also be used in combination with other inducers.
When nitric acid is used alone as an inducer, the addition amount is 1% -10%.
When the inducer is urea, oxalic acid, citric acid, malic acid or their salts, etc., the addition amount is 1% -10%.
The addition site of the inducer is not particularly limited as long as a constant concentration is maintained in the mother liquor in the crystallization apparatus. For example, the inducer may be added from a tank for dissolving ammonium sulfate, a storage tank for storing a mother solution of ammonium sulfate, an in-line as a crystallization apparatus, or the like. The place where the reducing agent is added for lowering the oxidation-reduction potential and the place where the sulfuric acid is added for increasing the free sulfuric acid concentration are the same as the place where the inducer is added.
The redox potential of the solution is 300mV or less, preferably 250mV or less, more preferably 200mV or less. When the redox potential exceeds 300mV, the effect of the inducer is significantly reduced and the shape of the crystals is likely to be prismatic rather than spherical. The inventor researches and discovers that the effect of the inducer can be obviously improved by reducing the oxidation-reduction potential regardless of the type of the inducer.
The method of lowering the oxidation-reduction potential may be any method. There are methods of adding a reducing agent or mixing with a very low redox potential. The reducing agent can be selected from: hydrogen sulfide, ammonium bisulfide, sodium bisulfide, potassium bisulfide, ammonium sulfide, sodium sulfide, potassium sulfide, sulfurous acid gas or ammonium sulfite, sodium sulfite, potassium sulfite, hydrazines, etc., as long as the quality of ammonium sulfide is not greatly affected.
The crystallization method of the ammonium sulfate solution may be concentration or cooling.
The crystallization method of the ammonium sulfate solution may be a continuous, semi-continuous or batch method.
The crystallization apparatus used for crystallization may be of any classification type, for example, a krystal-Oslo type, a stirred tank type, a DTB type, or the like.
And after ammonium sulfate crystals precipitated from the ammonium sulfate solution are separated, the ammonium sulfate mother liquor is recycled. The ammonium sulfate mother liquor is good for dissolving ammonium sulfate.
Compared with the prior art, the method for preparing granular ammonium sulfate provided by the invention has the following beneficial effects:
(1) the granular ammonium sulfate prepared by the method provided by the invention is large, round and high-quality, the axial ratio is as low as 0.7-1.5, and compared with the existing granular ammonium sulfate which is difficult to use such as angular column, powder and irregular, when the granular ammonium sulfate is used alone, the granular ammonium sulfate is small in dispersion and can be uniformly scattered under the condition of wind without being stuck to leaves and stems;
(2) when the granular ammonium sulfate prepared by the method is mixed with phosphate fertilizer, potash fertilizer and the like for use, the granular ammonium sulfate can be uniformly mixed with the phosphate fertilizer and the potash fertilizer, and the granular ammonium sulfate has consistent granularity and is convenient for uniform sowing.
Drawings
FIG. 1 is a schematic view of the production process of the present invention.
In the figure, 1, a dissolution tank; 2. a saturated solution; 3. a stirrer; 4. a throwing port; 5. crystallizing ammonium sulfate; 6. a first supernatant mother liquor; 7. a cooler; 8. a crystallization tank; 9. precipitating ammonium sulfate crystals; 10. a pipeline; 11. a second supernatant liquor; 12. a circulation pump; 13. a separator; 14. a granular ammonium sulfate product; 15. filtering the ammonium sulfate mother liquor.
Detailed Description
The present invention is described in detail with reference to the following specific embodiments, but the scope of the present invention is not limited to the specific scope of the present invention, and all other embodiments obtained by those skilled in the art without any inventive work based on the embodiments of the present invention belong to the scope of the present invention.
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